Muffler for an exhaust system of vehicle

ABSTRACT

Disclosed is a muffler for an exhaust system of a vehicle, which improves fuel efficiency through weight reduction and reduces deterioration of peripheral components. To this end, the present provides a muffler for an exhaust system of a vehicle. More specifically, the muffler includes a triple-material hollow casing, in which an outer layer formed of a plastic material and disposed on the outermost surface of the muffler, an intermediate insulating layer disposed on the inside of the outer layer and containing an aerogel material, and an inner layer formed of a stainless steel material and disposed on the inside of the intermediate insulating layer are stacked.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119(a) the benefit of Korean Patent Application No. 10-2011-0088536 filed Sep. 1, 2011, the entire contents of which are incorporated herein by reference.

BACKGROUND

(a) Technical Field

The present disclosure relates to a muffler for an exhaust system of a vehicle. More particularly, it relates to a muffler for an exhaust system of a vehicle, which can improve fuel efficiency through weight reduction and reduced deterioration of peripheral components.

(b) Background Art

Mufflers are typically installed along the exhaust line as part of the exhaust system of an internal combustion engine or any engine of a motorized vehicle. The muffler reduces exhaust noise through absorption techniques. In particular, the engine exhaust is routed through a series of passages and chambers lined typically with roving fiberglass wool and/or resonating chambers tuned to cause reflected waves that interfere with each other or cancel each other out.

Most conventional mufflers are made of a metal material to withstand high temperature exhaust gas while reducing noise produced during engine combustion. More specifically, they are often made of a stainless steel material to prevent or slow corrosion due to the high temperature and moister environment. These conventional mufflers structurally have an internal space that is divided into a plurality of chambers by a plurality of partitions (baffles) to improve the attenuation of exhaust noise so that exhaust noise can be gradually attenuated by interference of sound waves, reduction of pressure fluctuations, reduction of exhaust temperature, etc., while passing through the chambers of the muffler.

However, the conventional mufflers are made of a stainless steel. Stainless steel has high thermal conductivity, thus, the high temperature of the exhaust gas is transferred to the component surrounding the muffler (such as a lower vehicle body, fuel tank, etc.) via convection, radiation, or conduction, thereby causing deterioration of the surrounding components as a result. Moreover, despite the use of stainless steel materials, external corrosion is often caused by the high temperature exhaust gas and by external corrosion promoting substances such as salt water created from deicing salt used in the winter, etc. Furthermore, perforation corrosion is caused by condensation water, which leads to loss of the attenuation functions of the muffler, thereby rendering the muffler unaffected.

Therefore, to solve the above-described problems of the conventional muffler, a plastic muffler employing a plastic casing 1 has been proposed (see FIG. 3). However, plastic mufflers absorb sound through glass fibers are used as insulating and sound absorbing materials. These types of mufflers are effective in reducing high-frequency noise but are ineffective to low-frequency noise. In particular, the noise tuning corresponding to the vibration frequency (Hz) of the engine and the engine rpm is limited. Moreover, a large amount of expensive glass fibers must be used as insulating and sound absorbing materials. Additionally, the glass fibers may cause various problems such as deterioration of assemblability, environmental pollution, difficulties in mass production, etc. Furthermore, plastic mufflers have a structure in which the exhaust gas is in direct contact with the plastic casing, and thus the plastic casing may melt while vehicle running.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY OF THE DISCLOSURE

The present invention provides a noise tunable muffler for an exhaust system of a vehicle, which prevents deterioration of peripheral components due to high temperature exhaust gas, prevents loss of function due to external corrosion, and improves fuel efficiency through weight reduction.

In one aspect, the present invention provides a muffler for an exhaust system of a vehicle, the muffler comprising a triple-material hollow casing, in which an outer layer formed of a plastic material and disposed on the outermost surface of the muffler, an intermediate insulating layer disposed on the inside of the outer layer and containing an aerogel material, and an inner layer formed of a stainless steel material and disposed on the inside of the intermediate insulating layer are stacked.

In some embodiments, the intermediate insulating layer may be made of a nonwoven fabric impregnated with an aerogel. Additionally, the intermediate insulating layer may have a thickness of 1 to 20 mm depending on the temperature of exhaust gas.

In some embodiments, the outer layer may comprise a mixture of a plastic material and a reinforcing material. More specifically, the mixture may comprise 30 to 95 wt % of a plastic material and 5 to 70 wt % of a reinforcing material. In addition, the reinforcing material may have a ratio of length to diameter of at least 30.

In a further preferred embodiment, the casing may comprise first and second baffles for dividing the internal space into first to third chambers, an exhaust gas input pipe coming from the front of the casing, supported by the first and second baffles, passing through the first and second chambers, and extending to the third chamber, and an exhaust gas output pipe supported by the second baffle, passing through the second and third chambers, and going to the rear of the casing.

Other aspects and preferred embodiments of the invention are discussed infra.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a diagram showing a typical muffler provided in an exhaust line of a vehicle.

FIG. 2 is a cross-sectional view of a muffler for an exhaust system of a vehicle in accordance with a preferred embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional muffler for an exhaust system of a vehicle with a plastic casing.

Reference numerals set forth in the Drawings includes reference to the following elements as further discussed below:

-   -   10: casing     -   11: outer layer     -   12: intermediate insulating layer     -   13: inner layer     -   15: exhaust gas input pipe     -   17: exhaust gas output pipe     -   21: first chamber     -   22: second chamber     -   23: third chamber     -   31: first baffle     -   32: second baffle     -   34: perforation aperture

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

The present invention provides a muffler for an exhaust system of a vehicle, which is provided in an exhaust line, the muffler being characterized with a triple-material muffler casing and a noise tuning structure, which can improve fuel efficiency through weight reduction and reduced deterioration of peripheral components.

Referring to FIG. 2, a muffler for an exhaust system of a vehicle in accordance with an exemplary embodiment of the present invention comprises a triple-material hollow casing 10, in which an outer layer 11, an intermediate insulating layer 12, and an inner layer 13 are stacked together to form the tri-material casing. More specifically, the outer layer 11 is formed of a plastic material and is disposed on the outermost surface of the muffler. The intermediate insulating layer 12 is disposed on the inside of the outer layer 11 and is formed of (or containing) an aerogel. The inner layer 13 is formed of a stainless steel material and is disposed on the inside of the intermediate insulating layer 12. Moreover, an expansion/resonance type noise tuning structure, which is the same as a conventional muffler, is applied to the inner layer 13.

In more detail, the outer layer 11 is formed in substantially a box shape using a heat-resistant thermosetting or thermoplastic plastic material so as to prevent corrosion due to corrosion promoting substances and high temperature exhaust gas and to reduce the weight of the muffler by the use of plastic material. The outer layer 11 may be formed of polypropylene, polyethylene, polyamide, polyphenylene sulfide, polybutylene terephthalate, etc. without limitation by general injection molding or press molding. Any material, which does not deteriorate due to the thickness of the intermediate insulating layer 12 and the adiabatic temperature, can be used as the material for the outer layer 11.

Preferably, the outer layer 11 may include a reinforcing material to achieve noise reduction performance and improve component stiffness. In detail, the outer layer 11 may comprise a mixture of a plastic material and a reinforcing material and, preferably, may comprise 30 to 95 wt % of a plastic material and 5 to 70 wt % of a reinforcing material.

Examples of the reinforcing material may include, but are not limited to, glass fibers, mineral fibers, biofibers, carbon fibers, nanoclays, etc. having a ratio of length to diameter of at least 30. That is, the length of the reinforcing material is at least 30 times the diameter of the reinforcing material, and the reinforcing material may be formed by various processes such as general injection molding, press molding, etc.

The contents of the reinforcing material may vary within the above range depending on the temperature of the exhaust gas. If the content of the reinforcing material is less than 5 wt %, the heat resistance, strength and stiffness of the material are reduced, and thus the outer layer 11 may be easily melted down or broken down. Whereas, if it exceeds 70 wt %, the injection moldability or press moldability is reduced during manufacturing, the brittleness is increased, and thus the outer layer 11 may be easily broken due to external shock to the casing.

Also, as shown in FIG. 2, the intermediate insulating layer 12 is formed in substantially a box shape to be stacked on the inner wall of the outer layer 11 and may have a thickness of 1 to 20 mm depending on the temperature of the exhaust gas. The intermediate insulating layer 12 may be formed of a nonwoven fabric impregnated with a nano-sized aerogel to improve sound-absorbing and heat-insulating properties.

Typically, aerogels are materials having a large specific surface area, a high porosity, and a low density, and are prepared by drying a wet gel obtained by a sol-gel reaction under supercritical conditions where no gas-liquid interface exists such that the pore structure of the wet gel remains unchanged. Superfine fibers, about 1/10,000 the thickness of a human hair, are entangled together in the aerogel and thus about 90 to 99.8% air is trapped in the superfine fibers. As a result, the aerogel has an insulating effect about 40 times higher than that of glass fibers and a thermal conductivity about 2 times lower than that of polymer foams.

In this embodiment of the present invention, the intermediate insulating layer 12 is prepared in such a manner that a nonwoven fabric is impregnated with a nano-sized silica aerogel and then the resulting nonwoven fabric is dried under supercritical carbon dioxide conditions. As a result, the intermediate insulating layer 12 includes a nonwoven fabric impregnated with (or containing) an aerogel.

The inner layer 13 is formed of a stainless steel material into a substantially box shape to be stacked on the inner wall of the intermediate insulating layer 12. Meanwhile, the vehicle muffler according to the present invention has a noise tuning structure, i.e., an expansion/resonance type noise tuning structure, which is the same as a conventional muffler formed of a stainless steel material, thereby reducing low-frequency radiated noise as well as high-frequency radiated noise.

Accordingly, the triple-material casing 10, which is formed of a plastic material, a nonwoven fabric impregnated with an aerogel, and a stainless steel material, comprises first and second baffles 31 and 32 for dividing the internal space into first to third chambers 21 to 23, an exhaust gas input pipe 15 coming from the front of the casing 10, supported by the first and second baffles 31 and 32, passing through the first and second chambers 21 and 22, and extending to the third chamber 23, and an exhaust gas output pipe 17 supported by the second baffle 32, passing through the second and third chambers 22 and 23, and going to the rear of the casing 10.

Moreover, at least one perforation aperture 34 is formed on the second baffle 32 or on the first and second baffles 31 and 32 to facilitate the flow of the exhaust gas (flowing from the exhaust gas input pipe to the exhaust gas output pipe) introduced into the casing 10 and to increase the noise reduction effect.

In detail, the first and second baffles 31 and 32 are spaced from each other in the internal space of the casing 10, and the internal space of the casing 10 is sequentially divided into the first to third chambers 21 to 23 from the front to the rear. The exhaust gas input pipe 15 serves to inject the exhaust gas discharged from the engine through the exhaust line into the internal space of the casing 10. The exhaust gas input pipe 15 is accessed from the front of the casing 10 into the internal space of the casing 10 and its front end projects to the front of the casing 10.

The exhaust gas output pipe 17 penetrates the first chamber 21 in the internal space of the casing 10 to be supported by the first baffle 31 and penetrates the second chamber 22 such that its rear end is supported by the second baffle 32 and extends to the third chamber 23. The exhaust gas output pipe 17 serves to discharge the exhaust gas introduced into the casing 10 to the outside. The exhaust gas output pipe 17 is supported by the second baffle 32 in the internal space of the casing 10, passes through the second and third chambers 22 and 23, and then goes to the rear of the casing 10. That is, the front end of the exhaust gas output pipe 17 passes through the second chamber 22 to be supported by the second baffle 32 and passes through the third chamber 23 such that the rear end of the exhaust gas output pipe 17 projects to the rear of the casing 10.

As such, the muffler according to the present invention has a structure in which the internal space is divided into several chambers 21, 22 and 23 by the plurality of baffles 31 and 32 to attenuate the exhaust noise, and thus the exhaust noise can be gradually attenuated by interference of sound waves, reduction of pressure fluctuations, reduction of exhaust temperature, etc., while passing through the chambers of the muffler. The above-described noise tuning structure can effectively reduce the radiated noise due to the exhaust gas by disposing the first and second baffles 31 and 32 in appropriate positions of the casing 10.

Moreover, it is possible to effectively reduce the radiated noise due to the exhaust gas by changing the size and/or position of the pipes 15 and 17, for example, or by changing at least one of the position, number, and/or size of the perforation apertures 34, thereby optimizing the noise tuning. Furthermore, other than the pipes 15 and 17, an additional pipe may be provided such that the exhaust gas does not sequentially pass through the chambers 21 to 23, but is collected in any one of the chambers 21 to 23 to cause sound wave cancellation, thereby reducing the noise. Thus, the number of the chambers 21 to 23 and the pipes 15 and 17, provided to effectively perform the noise reduction for each type of engine, rpm and Hz, is not limited, and the exhaust gas doe not necessarily flow sequentially in one direction.

In this preferred embodiment of the present invention, when the above-described noise tuning structure is adopted in the casing 10, the intermediate insulating layer 12 formed of a nonwoven fabric impregnated with an aerogel is disposed between the outer layer 11 formed of a plastic material and the inner layer 13 formed of a stainless steel material such that the high temperature of the surface of the inner layer 13 due to high temperature exhaust gas is prevented from being transferred to the outside, thereby preventing deterioration of the plastic outer layer 11 disposed on the outermost surface of the muffler and the peripheral components. As a result, it is possible to reduce the two layers of the existing muffler, formed of a stainless steel material (corresponding to the inner layer of the present invention), into a single layer, i.e., the single internal/inner layer 13. However, the casing may be formed of at least two layers, if necessary.

Furthermore, in the present invention, the noise tuning structure provided in the casing is not limited to the above-described noise tuning structure and may be variously changed to well known noise tuning structures.

With the above-described configuration, the volume (or size) of the muffler according to the present invention can be significantly reduced, and the muffler according to the present invention reduces low-frequency radiated noise as well as high-frequency radiated noise through the existing expansion/resonance type noise tuning structure. In particular, it is possible to perform the noise tuning for each frequency band and for each engine rpm, and thus it is possible to reduce low-frequency booming noise and flow-induced noise in the high frequency band of 600 Hz or higher.

Typically, the booming noise may deteriorate somewhat due to a reduction in volume of the muffler, compared to the existing muffler. However, in the present invention, with the use of the triple-material casing 10, the radiated noise of the muffler can be reduced, and thus the overall noise reduction performance is equal to or higher than that of the existing muffler. Moreover, with the use of the intermediate insulating layer formed of a nonwoven fabric impregnated with an aerogel as an insulating material, the muffler according to the present invention has insulating properties about three times better than that of widely used insulating materials such as urethane foam or glass fiber of the same thickness. Thus, it is possible to reduce the thickness of the insulating material (i.e., the intermediate insulating layer) to about one-third of the original thickness while having the same insulating performance. As a result, the assemblability is improved, and the degree of freedom in design of peripheral components is increased.

Furthermore, since the surface temperature of the muffler due to the exhaust gas reaches a maximum of 400° C. in the exhaust system, the use of organic insulating materials is limited, and thus inorganic insulating materials such as glass fiber are most widely used. However, in the present invention, the organic nonwoven fabric impregnated with an aerogel having a heat resistant temperature of 600° C. or higher is used as the insulating material, and thus it is possible to prevent the insulating material (i.e., the intermediate insulating layer) from being melted or deteriorating. In addition, with the improved heat-resistant performance, it is possible to prevent external corrosion of the casing 10 due to its anti-rust properties.

As further evidence, the following evaluation tests were performed on the muffler according to the present invention.

1. Evaluation of Noise Performance

A prototype muffler with a triple-material casing (A) according to the present invention was prepared using a thermoplastic material, PA6+GF35% (a mixed material of polyamide 6 and glass fiber), and a conventional muffler with a stainless steel casing (B) was prepared as a comparative product.

The thus prepared prototype muffler (A) and conventional muffler (B) were tested for noise performance with the same volume to eliminate the difference in noise performance due to a difference in volume and mounted in vehicles. As a result, the radiated noise of the prototype muffler (A) was measured as 2 to 3 dBA lower than that of the conventional muffler (B) in a region of 3,000 to 4,000 rpm and also measured as 7 to 10 dBC lower than that of the conventional muffler (B) in the high speed booming noise region of more than 3,000 rpm, from which it can be seen that the muffler according to the present invention has improved the noise performance compared to the conventional muffler.

2. Evaluation of Exhaust Pressure

The exhaust pressure resistance of a prototype muffler with a 17 L triple-material casing according to the present invention was measured and compared with that of a conventional muffler with a 21 L stainless steel casing. As a result, it can be seen that the exhaust pressure resistance of the conventional muffler was 35.8 kPa, but that of the prototype muffler according to the present invention was reduced to 32.3 kPa. If the exhaust pressure is reduced, the output of the engine is increased, thereby improving the fuel efficiency.

3. Evaluation of Drainage Performance

Evaluation of drainage performance was tested to evaluate the anti-corrosion properties of the muffler in the present invention against condensation water. After a predetermined amount of water was fed into the casing of the prototype muffler according to the present invention, the residual water was measured five minutes after the engine was started. The content of residual water measured was 0 cc, from which it can be seen that the probability of condensation water is very low.

4. Durability Test of Pipe Joints

After applying a vibration of 0.5 to 30 Hz for 300 seconds to a joint between the casing and the exhaust gas input pipe and that between the casing and the exhaust gas output pipe of the prototype muffler according to the present invention, the degree of deformation was measured to within 6%, which was one-third of the failure criteria, from which it can be seen that the durability was excellent.

As described above, the muffler for an exhaust system of a vehicle according to the present invention includes a casing formed of a heat-resistant plastic material and an aerogel material having heat-insulating properties, and thus it is possible to reduce the weight and volume of the muffler. As a result, it is possible to improve the fuel efficiency, the assemblability, and the degree of freedom in design of peripheral components. Moreover, the muffler of the present invention prevents deterioration of peripheral components from high temperature exhaust gas, prevents loss of function due to external corrosion, and effectively reduces low-frequency radiated noise as well as high-frequency radiated noise through effective noise tuning.

The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. 

1. A muffler for an exhaust system of a vehicle, the muffler comprising a triple-material hollow casing made up of at least three stacked layers, wherein the at least three stacked layers includes: an outer layer formed of a plastic material and disposed on the outermost surface of the muffler, an intermediate insulating layer disposed on the inside of the outer layer and containing an aerogel material, and an inner layer formed of a stainless steel material and disposed on the inside of the intermediate insulating layer.
 2. The muffler of claim 1, wherein the intermediate insulating layer comprises a nonwoven fabric impregnated with the aerogel.
 3. The muffler of claim 1, wherein the intermediate insulating layer has a thickness of 1 to 20 mm depending on the temperature of exhaust gas.
 4. The muffler of claim 1, wherein the outer layer comprises a mixture of a plastic material and a reinforcing material.
 5. The muffler of claim 1, wherein the outer layer comprises 30 to 95 wt % of a plastic material and 5 to 70 wt % of a reinforcing material.
 6. The muffler of claim 5, wherein the reinforcing material has a ratio of length to diameter of at least
 30. 7. The muffler of claim 1, wherein the casing comprises first and second baffles for dividing the internal space into first to third chambers, an exhaust gas input pipe coming from the front of the case, supported by the first and second baffles, passing through the first and second chambers, and extending to the third chamber, and an exhaust gas output pipe supported by the second baffle, passing through the second and third chambers, and going to the rear of the casing.
 8. An exhaust system for a vehicle, comprising an exhaust line configured to route and remove exhaust from an engine; and a muffler disposed within the exhaust line, wherein the muffler includes a casing made up of at least three stacked layers, the at least three stacked layers including: a first layer made of a plastic material and disposed on the outermost surface of the muffler casing, an intermediate insulating layer disposed on the inside of the outer layer and containing at least an aerogel material, and an inner layer made of a stainless steel material and disposed on the inside of the intermediate insulating layer.
 9. The muffler of claim 10, wherein the intermediate insulating layer comprises a nonwoven fabric impregnated with the aerogel.
 10. The muffler of claim 10, wherein the intermediate insulating layer has a thickness of 1 to 20 mm depending on the temperature of exhaust gas.
 11. The muffler of claim 11, wherein the outer layer comprises a mixture of a plastic material and a reinforcing material.
 12. The muffler of claim 11, wherein the outer layer comprises 30 to 95 wt % of a plastic material and 5 to 70 wt % of a reinforcing material.
 13. The muffler of claim 12, wherein the reinforcing material has a ratio of length to diameter of at least
 30. 14. The muffler of claim 11, wherein the casing comprises first and second baffles for dividing the internal space into first to third chambers, an exhaust gas input pipe coming from the front of the case, supported by the first and second baffles, passing through the first and second chambers, and extending to the third chamber, and an exhaust gas output pipe supported by the second baffle, passing through the second and third chambers, and going to the rear of the casing. 